ok, so i picked up my first a4 today, a 98 1.8t quattro. got it pretty cheap because the po thought it has a blown head gasket..
it was running like crap too, but i traced that down to a couple vacuum leaks
Then i check the oil cap and the dipstick, see no signs of water, and so i look in the coolant reservoir, it looks pretty nasty. decide to take the upper rad hose off to see if i can put some water in there for a test drive, remove the clamp and glub glub blub out comes chocolate pudding all over my alternator!

so, from what i have found searching its either the head gasket, or the oil cooler. any wagers?
its got 184k on the clock, and the po claims it was maintained pretty well just got hot one day and puked out of the overflow, so is it possible for it to be a head gasket that only pushes oil into the coolant, and not the other way? I will do a compression test in the A.M. but im leaning toward the oil cooler myself. how hard is it to remove?

 

or maybe could be green coolant caused sluge?
see photos
sludge on my finger


this is in a grey plastic sack. the camera flash makes it look slightly lighter in color than it looked in person in my dark garage


this is what it looks like on a paper towel

 

shouldn't be any green coolant anywhere near the engine

 

Probably the head gasket. They are normally never an issue with 1.8Ts, but at that mileage and seeing those pics idk... Oil coolers are cheap though. Start with replacing it and doing a GOOD coolant flush. Use whatever coolant you want as long as it's one type and not a mixture of oem g12 and universal green stuff. Oil cooler is simple. Take the oil filter off, remove two hoses and take it out by removing the center nut and watch out for the seal.

 

I say oil cooler. If it was the headgasket it would probably still be running bad with a smokey exhaust smelling like coolant.

 

ok, so i went and got a harbor freight compression tester, and all cylinders showed about 150psi.. sounds a little low, but they were all pretty much the same.
next i took the oil cooler off and plugged one water inlet, while blowing into the other as hard as i could without passing out, and i saw no sign of leakage there. do i need more pressure?
so im wondering if it could be from somebody mixing coolant types?
the sludge in there is a light brown really thick crap.

Is it possible for a head gasket to fail and only push oil into the coolant? there is no water in the oil, and no smoke from the tailpipe?

 

so before work this morning i went out to the garage and whipped together a way to pressure test the oil cooler in a bucket of water.. sure enough, blub blub blub of air coming out of the middle under about 50psi.
got one coming in the mail asap

So now i just need to get all the crap flushed out of the system.
I am thinking i need to get the thermostat out and add some simple green and just keep fill, run it, flush and repeat?

 

Today I noticed my oil pressure seemed to be low, so I checked my oil and wow it was down about 1 and 1/2 litres. I topped it up and thought wow that's a big jump. So I go back out and have a look under the hood and the coolant looks like it's mixed half and half with oil.
I'm thinking danm the head gasket is gone or worse both....lol.
Then I start searching the net and come across this.
What is the best way to check the oil cooler?
What happens when you mix the Red coolant with the green coolant?

 

I dont know of any way to check the oil cooler without removing it from the car.
If your car is running fine otherwise i would highly suspect the oil cooler.
when i checked it i removed it and left the coolant lines attached. then i plugged the one coolant line and put about 30 psi in the other side. I had the cooler sitting in a bucket of water, and there were a lot of bubbles coming out.

Whatever your case, dont drive it in its current condition!
if you have oil mixing with the coolant, it turns into sludge, and will soon cause you to overheat, and will sludge up all over in the coolant system.
It took me a LONG time to get all the junk flushed out of my system after i got the new oil cooler on.